Endoscopic instruments have been developed to allow physicians and surgeons to view conditions within the body and perform certain surgical procedures without the trauma, disfiguration, expense, and hazards usually associated with conventional types of surgery performed through relatively large incisions in the skin.
Endoscopes range in complexity from simple viewing scopes (employing a light source and a system of conventional lenses to transmit the image) to relatively complex endoscopes (having a light source, an image guide, several fluid channels, and a surgical tool channel). The number of features employed in an endoscope is determined in part by the requirements of the surgical specialty in which the endoscope is used and in part by the size of endoscope which can be accommodated by the body part through which the endoscope will be introduced. The light source for illuminating the site of interest is usually positioned outside the patient's body to avoid overheating the tissues. The light is communicated through the endoscope by an illumination or light guide usually formed of a fiber optic bundle. It is conceivable that the light guide could be separate from the endoscope itself. This would reduce the diameter of the endoscope or would allow additional functions in a scope of a given diameter. However, difficulties might be encountered in coordinating the positions of the light guide and the endoscope in some situations.
Endoscopes may be constructed as rigid or flexible as conditions require. The use of conventional lenses to form the image guide generally requires that the scope be rigid or semi-rigid. Flexible endoscopes employ coherent optical fiber bundles wherein the opposite ends of the fibers are identically ordered. The image quality of lens based image guides is generally superior to image guides formed of optical fibers. However, the convenience of a flexible endoscope compensates for the slight loss in resolution.
The fluid channels in endoscopes serve varied purposes. In some endoscopes for use in lungs, for example, an air passage is required to allow the lung to breathe. In certain procedures, a gas or a liquid is used to insufflate or inflate a cavity in the body for better access and a better view. In many cases, a supply of cleansing fluid such as water is used to clear away a body fluid such as blood from a location to facilitate inspection or to clean the image guide objective lens that has become smeared. A vacuum line is often provided for removing fluids from the site. The surgical tool channel provides for the insertion of various implements through the endoscope such as forceps, scissors, punches, coagulating electrodes, and the like.
A typical endoscope may include a tubular sheath connected to a frame or mechanical coupling to which viewer optics are connected. Fluid channels extending through the sheath communicate with external fluid connections on the frame and usually include valves therebetween. A tool port on the frame communicates with a tool channel in the sheath and might include a clamp to hold the tool in place. A light port connects with and receives light from a light source. The light is transmitted from the viewing end or proximal end of the endoscope to a light directing lens or lenses at the distal end. The objective lens and possibly other optical elements are positioned at the distal end and pass the image to the image guide. The objective lens is usually fixed and may be oriented along the longitudinal axis of the sheath or be angled off-axis for a view to the side. The image passes from the image guide to the viewer section of the endoscope through which the physician views the site of interest. Some endoscopes have a fixed combination of functions. Others are adapted to allow a selection of functions from a variety of surgical tools and viewing angles. In any case, endoscopes are constructed so as to allow thorough sterilization.
The viewer sections of endoscopes usually accommodate adapters for connecting motion and still cameras and video cameras. In some cases, an image splitter is employed to direct part of the image to an optical viewer for direct viewing and another part to a video camera to televise a procedure for training purposes or to record the operation or exploration for comparison with explorations from other times in the course of a treatment. However, the use of an image splitter offers a somewhat degraded pair of images for a given level of light since the light levels are divided by the image splitter.